There have been a variety of different types and kinds of retractable tower antenna masts used for a variety of purposes. In this regard, the antenna mast is a mast having an antenna, such as a radio frequency antenna, mounted at the top end thereof. The mast can be retractable, wherein the mast can be retracted into a storage position in which the mast is relatively short in its overall height dimension. Alternatively, the retractable mast can be lengthened by causing it to move extensively upwardly into a fully extended or deployed use position where the overall height is many times larger than its retracted storage height dimension.
One example of a retractable tower antenna mast was one which could be driven between a storage height of approximately 30 feet and a fully deployed height of approximately 90 feet. Such a unit had three telescoping steel tubular sections. In its use position, the fully extended upright antenna mast was not perfectly erect and would tend to lean in one direction. Such a leaning attitude is not entirely satisfactory for many applications due to its inherent structural instability. Furthermore, such a large heavy unit would deploy slowly. For example, such a four section steel mast would deploy from a 30 foot nested position to a 90 foot deployed position, in about 15 minutes.
Thus, such a heavy and unwieldly antenna mast would not at all be satisfactory for other applications, such as for use on a vehicle for use in mobile communications, such as broadcast microwave systems used by television reporters relaying current news event reports to a broadcast station. For such an application, the antenna mast is mounted on a light-weight vehicle, such as a van. The mast must necessarily be relatively light in weight, and thus cannot be made of heavy materials such as steel. Also, the mast must be stored in a nested or a storage position in a compact configuration such as a height of no more than approximately eight feet. This is important because when the vehicle is traveling from place to place, the nested or stored antenna mast mounted on top of the vehicle must be able to pass under bridges or other overpass structures along the roadway.
Such light-weight mobile antenna masts have employed pneumatic actuators to deploy them. In this regard, an on-board air compressor unit is employed to move the mast between its storage and use positions. However, the pneumatic system was not at all satisfactory for many applications, since it operated quite slowly. In this regard, the air compressor required an undesirably long period of time to develop sufficient pressure to raise the antenna mast. Also, in many adverse climate conditions, such as cold weather conditions, the pneumatic system did not function at all satisfactorily. Furthermore, seals would wear at an undesirably fast rate. Additionally, the pneumatic systems release too slowly, and thus the mast would retract very slowly and thus required an unduly long waiting period.
Therefore, it would be highly desirable to have a new and improved antenna mast which could deploy very rapidly, such as in a time period of under one minute. Also, such a new and improved antenna mast should be structurally stable when disposed in its fully extended upright position. This is particularly important with light-weight masts which may be used in adverse climate conditions including high winds and snow and ice conditions.